The proposed research deals with the following aspects of sarcoplasmic reticulum structure and function. 1. The biosynthesis of sarcoplasmic reticulum (SR). The regulation of the biosynthesis of the Ca2 ion transport ATPase of SR will be analyzed in cell-free systems, in tissue culture and in living animals. The role of intracellular free Ca2 ion in the regulation of gene-expression will be tested at the transcriptional and translational level. The Ca2 ion transport ATPase content of red and white skeletal and cardiac muscles will be determined by biochemical and electron microscope techniques. The possibility of structural and kinetic differences between ATPases isolated from slow, and fast skeletal muscles will be explored to establish whether innervation influences the expression of different Ca2 ion-ATPase isoenzymes in different muscles. 2. The Ca2 ion release from sarcoplasmic reticulum. The Ca2 ion permeability of pure sarcoplasmic reticulum vesicles and functionally competent isolated triad elements will be analyzed in response to membrane potential. 3. The mechanism of Ca2 ion transport will be studied with respect to the mode of involvement of phospholipids and proteolipids, and the role of Mg2 ion and K ion as counterions in Ca2 ion transport. 4. Work will be continued on the primary structure of the proteolipid isolated from rabbit skeletal muscle and on the Ca2 ion transport ATPase of cardiac muscle.